Manufacture of magnesium



July 14, 1942.

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I Ca/cium carbide formaf/on I firino'ingI N. R. COLLINS ET ALMANUFACTURE OF MAGNESIUM Filed March 28, 1941 I (a/cining ,7

Cake or'caroon 2 Sheets-Sheet l Magnesium compound such as magnesiumhydroxide brucife or magnesi/e I (fa/whiny /0 I Grinding I My -IT/zerma/ radar/ion I B lmpurifies and carbon (a/cium carbons/e J Pas/dueinc/uoing CaO C My 0 ioreening and nydrau/iq separaf/bn Carbona/ion a)/ow femperafure IMagnes/um carbona/e INVENTORS film/er H. 6/055 ATTORNEYy 1942- N. R. COLLINS ETAL 2,289,627

\ MANUFACTURE OF MAGNESIUM Filed March 28, 1941 2 Sheets-Sheet F IE E' Zirne /7 firuci/e 0r magneshe Coke or carbon I Ca/c/h/hy /0 C'a/c/umcarbide v formaf/on fig I Grind/r7; I

Gr/hd/hy l9 9 AWm /redud/bn I Pas/due l'nc/ud/hg C50 c My 0 Carbona/x'onC0? under pressure Ca/c/um 'carb ona/e MagnJs/um and carbon b/CarbonafeConversion fa basic carbons/e INVENTORS Gunfer H. 6/055 BY Ne i/ E.Coll/r15 L ATTORNEY j vide a process bodiment of Patented July 14, 1942Neil It. Collins, Los Altos, and Gunter H.

Belmont, Calil., assign Gloss,

ors to Marine Magnesium Products Corporation, South San Francision ofDelaware Application March 28, 1941, Serial No. 385,652 8 Claims. (01.75-457) co, CaliL, a corporat This invention relates generally to themanufacture' of metallic magnesium by thermal reduction of magnesiumcompounds such as magnesium oxide. More particularly, the inventionrelates to processes making use of thermal reduction of magnesium oxidewith calcium carbide.

It is an object of the invention toprovide an economical process for themanufacture of metallic magnesium from various sources of magnesiumcompounds available, such as brucite,

, rn'agnesite, or other inexpensive sources of magnesium compounds. a

A further object of the invention isto promaking possible utilization ofthe residue after thermal reduction of magnesium, oxide with the calciumcarbide.

Additional objects bf the invention will appear from the followingdescription in which the preferred embodiments have been set forth indetail in conjunction with the accompanying drawin s,

Referring to the drawings:

Figure l is a flow sheet illustrating one emthe invention; and FigureZis aflow sheet illustrating a'second I embodiment.

In the past it has been known that magnesium oxide can be reduced withcalcium carbide for the production of metallic magnesium. Such a processhas the advantage that the magnesium vapor evolved can be directlycondensed as a relatively pure metal. It has the disadvantags that arelatively large residue is obtained after the thermal reductionoperation which contains end products such as calcium oxide and carbon,together with amounts of unreacted calcium carbide and magnesium oxidedepending upon the efiiciency of the reaction. If this residue iswasted, it adds considerably to the cost of manufacture of the-metallicmagnesium. The present invention utilizes part or all of this residueback in the process.

Referring first to Figure 1, the process has been illustrated asutilizing a suitable magnesium compound, such as a magnesium hydroxide,natural brucite, or magnesite". This material is subjected to thecalcining operation l0, after which calcined material is subjected. togrinding H. The ground material is then intermixed with ground calciumcarbide in suitable proportions, and the mixture is then compressed intoellets or briquets, as indicated at l2. These briquets are then. chargedin a suitable retort for the thermal reduction operation l3.Thermalreduction of the charge is carried outat temperatures such asfrom 1050 to 1115 C., under a high ,vacuum such as 0.2 to 10 mm.. ofmercury. Where graphite or carborundum retorts are employed, one may usehigher temperatures and pressures, as understood in the art. Suitableequipment for this purpose is known and need not be described in detail.Briefly, the equipment includes a suitable furnace for heating theretort, together with means in conjunction with the retort forcondensing the evolved magnesium vapor.

The character of the residue left after thermal reduction is dependentsomewhat upon the ratio in which the ingredients are intermixed, and theefliciency of the reaction. In a typical instance,

the residue will consist of considerable amounts of calcium oxide andcarbon, which are end products of the reaction, together with someunreacted calcium carbide and magnesium oxide. To utilize this residue,it is subjected to slaking M, at a suitable temperature, such as 90 to100 0., after which the resulting slurry is subjected to the screeningand hydraulic separating operation it. This operation is for the purposeof removing oversized impurities and relatively heavy solid impuritiessuch as calcium silicate. It is desirable to effect removal of suchimpurities in order to prevent the building up of impurities in theprocess. The purified slurry from it is then subjected to separatingtreatment for the separate recovery of calcium and magnesium compounds.In Figure 1, the first step of this separating treatment is carbonationat a relatively low temperature as indicated at It, which involvescontact of the slurry with carbon dioxide at temperatures such as from16 to 18 C., whereby solid phase calcium and magnesium carbonates areproduced. The carbon dioxide is preferably supplied with another inertgas, such as airor flue gases. Such a carbon dioxide carrying gas shouldhave a of carbon dioxide, as for example about 10% by volume. Themagnesium carbonate is formed of particles relatively larger than theparticles of calcium carbonate, and therefore the desiredseparation canbe carried out by screening. The carbon present in the slurry beingcarbonated is in relatively finely divided form, and passes out with thecalcium carbonate. This mixtureis then utilized, as indicated, for themanufacture of calcium carbide for further use in the process. Thus, themixture of calcium carbonate and carbon is shown being'supplied to thecalcining operation H, in which it is desirable to burn the carboncontent to supply relatively small content part or all of the necessaryheat for'calcining. The resulting calcium oxide is supplied to theoperation l8, where it is reacted with coke or carbon for themanufacture ofcalcium carbide. This calcium carbide is then shown beingsubjected to grinding I! to .supply the ground material for the mixingand briquetting operation II. To take care of loss 01" calcium in thesystem, small additional or magnesite, without utilizing large amountsof lime. In many instances this will effect a substantial saving in thecost of manufacture of the metallic magnesium, because in localitieswhere brucite or magnesite may be available at low cost, lime may berelatively expensive.

The process of Figure 2 is similar to Figure 1 except that a diflerencein procedure is employed for carrying out a separating operation uponthe residue. Thus, in this instance after the residue has been subjectedto slaking I4 and screening and hydraulic separation l5, it is subjectedbon contents for forming calcium carbide for to carbonation underpressure (greater than at- I mospheric) at 21, which, as is known tothose skilled in the art, produces solid phase calcium carbonate andmagnesium bicarbonate in solution. The calcium carbonate is separatedfrom th bicarbonate solution by suitable means such as filtration ordecantation. A The carbon passes out with the calcium carbonate. Thecalcium carbonate and carbon are shown being supplied to the calciningoperation IT, as in Figure l.

The magnesium bicarbonate solution can be converted'to basic magnesiumcarbonate at stage 22,

as by releasing the pressure uponthe same and material can then betreated as a valuable byproduct of the process, or as indicated it canbe returned to the calcining operation ID for re-use in the process.

We claim:

1. In a process for the manufacture of magnesium, efiectingthermaLreduction of magnesium oxide with calcium carbide, separating outthe calcium and carbon contents from the residue of the reaction, andutilizing said separated calcium and carbon contents for the manufactureof calcium carbide for further cyclic use in the process.

2. In a process for the manufacture of ma nesium, effecting thermalreduction of magnesium oxide with calcium carbide, removing impuritiesfrom the residue, efiecting a separation of calcium and carbon contentsfrom the residue,

' and utilizing such separated calcium and carfurther cyclic use in theprocess.

3. In a process for the manufacture of magnesium, efiecting thermalreduction of magnesium oxide with calcium carbide, effecting aseparation between the calcium and magnesium contents of the residue toyield calcium and magnesium compounds, and reusing said calcium andmagnesium compounds in the process.

4. In, a process for the manufacture of magnesium, efiecting thermalreduction of magne-.

sium oxide with calcium carbide, effecting a separation uponthe residueof the reaction to yield separate calcium and magnesium compounds,utilizing the calcium compound for manufacture of calcium carbide forfurther cyclic use in the process, and utilizing the magnesium compoundfor supplying supplemental magnesium oxide for use in the thermalreduction operation.

5. In a process for the manufacture of magnesium, effecting thermalreduction of magnesium oxide with calcium carbide, slaking the residue,removing impurities from the slaked material, efiecting a separationupon the slak'ed material to yield separate calcium and magnesiumcompounds with separation of the carbon content together with thecalcium carbonate, and utilizing the separated calcium compound andcarbon for the manufacture of calcium carbide forfurther cyclic use inthe process. I

'6. In a process for the manufacture of magnesium, effecting thermalreduction of magnesium oxide with calcium carbide, slaking the residueof the reaction, removing impurities from the slaked material, eifectinga separation. upon the slaked material to yield separate calcium andmagnesium compounds, the carbon content of the residue being separatedout with the calheating it to an elevated temperature, and this with thecalcium compound for calcining the calcium compound to form calciumoxide, utilizing the calcium oxide thus obtained for the manufacture ofcalcium carbide for further cyclic use in the process, and utilizing theseparated magnesium compound for supplying magnesium oxide for furthercyclic use in the. process.

'7. In a process for the manufacture ofmagnesium, efi'ecting .thermalreduction of magnesium oxide with calcium carbide, efi'ecting aseparation between the calcium and magnesium contents of the residuetoyield calcium and magnesium compounds, and reusing said calcium compoundfor forming calcium carbide for further cyclic use in the process.

8. In a process for the manufacture of magnesium, effecting thermalreduction of magnesium oxide with calcium carbide to yield a residuehaving both'calcium and magnesium contents, removing a substantial partof the residual magnesium content from the residue, and then reusing theremaining part of the residue in the process.

NEIL R. COLLINS.

GUNTER, H. GLOSS.

